Panasonic VF2 WhisperFit ventilation fans are not only as energy efficient as conventional Panasonic Ceiling fans, but they are compatible with either 3 or 4 inch duct and are only 5.5 inches deep. Note that they are not quite as quiet as their larger Panasonic counterparts, but nearly so, As with other Panasonic fans these fans are rated for continuous operation, include a built-in backdraft damper, thermal fuse protection, and rust-proof paint on a galvanized steel body. They require a 10 3/8" mounting opening and have a grill that is 13 inches square. The grill trim is white. Voltage/Power: 120VAC 60Hz, 0.12 to 0.18 amps Approvals: UL Listed for use in a tub/shower with GFCI branch circuit wiring Model # Specs (FV05VF2), 3" duct: 50 cfm, 0.5 sones, 17 watts Mount: 10 7/8 sq. Model # Specs (FV05VF2), 4" duct: 50 cfm, 0.4 sones, 17 watts Model # Specs (FV-08VF2), 3" duct: 70 cfm, 0.8 sones, 24 watts: Mounts 10 7/8 sq. Model # Specs (FV-08VF2), 4" duct: 80 cfm, 0.8 sones, 24 watts Model # Specs (FV-11VF2), 3" duct: 90 cfm, 1.5 sones, 34 watts: Mounts 10 7/8 sq. Model # Specs (FV-11VF2), 4" duct: 110 cfm, 1.5 sones, 34 watts These fans will fit either 4" or 3" ducting - A adapter is included with each fan for 3" ducts. Our Panasonic Fan Customer Service Guarantee.